I think there might be alien life out there. Intelligent/sentient life, however, is a big leap of faith imo. It took 4.5 billion years for us to get here and the sun will make this planet uninhabitable in another billion or so years. Another thing is that our sun is pretty rare when it comes to stars, most stars are red dwarfs which, while having a lot longer lifespans, seem to be a lot more violent for a lot longer after forming and the planets need to be a lot closer to them for them for liquid water to exist which means said planets probably get the atmosphere stripped away by the solar storms way before the star calms down.